Adjustable tool inserts such as disclosed in U.S. Pat. Nos. 3,178,969 or 2,946,245 are installed in boring bars or the like with means such as readily accessible hex nut adjustment at the outer face of the insert for effecting precise adjustment while installed in the boring bar. It is known in the art in using such tools in a numerically controlled machine wherein a number of different tools are stored in a magazine for automatic selective installation in the spindle of the NC machine to effect adjustment to the individual tools in a gauging station separate from the NC machine. Adjustment settings may be made relative to a master part or other gauging surface prior to storage of the tools in the magazine of the NC machine and from time to time such tools may be removed from the magazine for servicing and readjustment. Dimensional variations from wear in the cutting tools or otherwise which may develop between successive cutting operations are known by post gauging operations or by periodic tool inspections which require removal from the magazine of the NC machine.